The present invention relates to a high voltage power source for supplying a DC high voltage to a discharge tube, such as a laser tube.
FIG. 3 is a block diagram exemplary of the conventional high voltage power source for the discharge tube, in which a high voltage power source 2 is provided with an oscillator circuit 4 which outputs an AC voltage on a basis of a DC or AC input voltage V1, a booster circuit 6 for boosting the AC voltage up to a predetermined high voltage, a rectifier circuit 8 for rectifying the boosted AC voltage and for supplying the output voltage (DC high voltage) V2 to a load consisting of a discharge tube 12, such as a lser tube, and a control circuit 10 which controls, for example, the oscillator circuit 4 to carry out constant-current control for a load current I flowing in the discharge tube 12.
The above-mentioned discharge tube 12, such as the laser tube, connected to the high voltage power source 2 is generally inferior to the high voltage power source 2 in lifetime or reliability.
The conventional high voltage power source 2, however, will continue outputting the high voltage V2 even when the discharge tube 12 is abnormal to lead to an abnormal operation of the system because the discharge tube 12 does not operate (non-oscillation for the laser tube) or deteriorates so as to be unstable in operation, which is dangerous for the system.